textproduct: Quad Cities

KEY MESSAGES

- A warm front will produce scattered thunderstorms (40-60% coverage) Saturday night into Sunday morning. There is a Marginal Risk (Level 1 out of 5) for severe storms. The primary hazards are hail and gusty winds.

- A pattern change this weekend will bring increasing heat and humidity to the area that is forecast to persist through next week. The probability of heat indices exceeding 100 degrees continues to increase (70-90% chance).

SHORT TERM /THROUGH SATURDAY/

Issued at 211 AM CDT Fri Jun 26 2026

A mid-level shortwave trough is going to pass to our south today, bringing along a low pressure system and warm front into northern Missouri. Isentropic upglide and WAA in the low levels plus mid- level F-gen will support scattered showers (30-50% coverage) south of Interstate 80 with a few rumbles of thunder possible (10-25%) along and south of Highway 34. According to the 26.00z REFS run, rainfall accumulations are forecasted to be light ranging from a couple hundredths along Interstate 80 to a two tenths of an inch south of Highway 34. Other model guidance shows higher amounts, but the dry low levels from the cold front yesterday will cut into rainfall rates. Easterly flow at the surface and cloud cover are expected to keep today on the cool side with highs in the mid-70s. By tonight, the low pressure shifts eastward into Illinois and Indiana as northeasterly flow advects in cooler, drier air, clearing out the skies. Lows will drop back into the mid-50s to low 60s.

Heading into Saturday, an unseasonably strong longwave trough (10-year average return interval according to CFSR climatology) digs into the western CONUS. This enables a ridge to build over the Mid-to-Upper Mississippi River Valley and pressure falls along the Front Range of the Rockies. Our winds will shift to out of the southeast during the day as the remnant boundary from today's system is pulled northward, setting the stage for shower and thunderstorm development heading into Saturday night.

LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/

Issued at 211 AM CDT Fri Jun 26 2026

Saturday Night-Sunday...As the warm front moves northward into our CWA, a fast band of scattered thunderstorms (40-60% coverage) will develop along the boundary. Strong WAA in the 925-850mb layer and a weak, ridge-riding trough could enable MUCAPE values to approach 2000 J/kg as sfc-to-500 mb bulk shear exceeds 30 knots along the front (60-80% joint probability per the 25.12z LREF run). This atmospheric profile would support elevated convection and a hail threat which is why the SPC has issued a Marginal Risk (Level 1 out of 5) for severe storms Saturday night into Sunday morning. One thing going for us though is the lack of upper-level dynamics which should suppress widespread convection, but the severe threat will be present with any storms that do develop. Regardless, dew points will likely (60-80%) soar into the mid-to-upper 70s behind the warm front, and by Sunday night, the warm front moves north of Highway 20, putting the entire CWA in the warm sector and underneath a ridge. This sets the stage for potential excessive heat heading into the beginning of next week.

Monday-Tuesday...The ridge holds firm on Monday as southerly flow and mostly clear skies allow heat indices to possibly exceed 100 degrees, warranting heat headlines (currently a 50-80% chance per the 25.12z LREF run). On Tuesday, bands of shear vorticity ahead of the longwave trough over the western CONUS is expected to weaken the northern extent of the ridge and introduce southwesterly flow aloft. This opens the door for trough passages later in the week, but the ridge should remain dominant over our CWA as heat headlines remain likely (60-90%) Tuesday.

Wednesday-Thursday...The middle of next week remains uncertain as a ring of fire could develop with the main ridge axis centered on the Ohio River Valley. Subtle bands of shear vorticity will ride around the ridge, forming MCSs across the Northern Plains and Great Lakes, and introducing PoPs to our northern CWA. This could cut into the heat risk north of Highway 30 while areas south keep heat headlines (70-90% chance) through Thursday.

AVIATION /18Z TAFS THROUGH 18Z SATURDAY/

Issued at 1239 PM CDT Fri Jun 26 2026

A storm system is exiting to the east early this afternoon and rain showers will slowly exit through 20 UTC at KBRL. MVFR conditions are possible in showers. Otherwise, VFR conditions are forecast through the remainder of the period. A period of MVFR clouds are possible after 00 UTC but confidence is low in this occurring.

DVN WATCHES/WARNINGS/ADVISORIES

IA...None. IL...None. MO...None.